Average Heat Transfer Coefficient Measurements in a Fuel Bundle: Method Development

Abstract

Measurement of single-phase heat transfer rates in a laboratory-scale rod bundle can aid in the design of a full-scale nuclear fuel bundle. It is desirable to obtain heat transfer coefficient measurements as a function of axial position with a high degree of measurement confidence. To achieve this goal, a heated calorimeter is designed and instrumented to measure power input and temperature. Temperature measurement is accomplished using thermocouples embedded in the calorimeter material, and a cartridge heater inserted concentrically in the calorimeter material creates a constant heat flux. The present study examines the contributions of the design parameters and uncertainties in the measurements to the overall uncertainty in the heat transfer coefficient. A design stage uncertainty analysis allows prediction of the required uncertainty in temperature difference measurement to achieve a desired uncertainty in the heat transfer coefficient. The experimental design for differential temperature calibration and representative uncertainty results are presented. All significant contributions to the total uncertainty in heat transfer coefficient are described and quantified.